From b432766202acec5c8414a7a3409d64807a652564 Mon Sep 17 00:00:00 2001
From: "jan.nijtmans" <nijtmans@users.sourceforge.net>
Date: Wed, 23 Nov 2022 12:15:24 +0000
Subject: Make "read" throwing a "illegal byte sequence" exception. Doesn't
 work for "gets" yet.

---
 generic/tclIO.c | 32 ++++++++++++++++++++++++++------
 tests/io.test   |  2 +-
 2 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/generic/tclIO.c b/generic/tclIO.c
index 652043c..f5344b3 100644
--- a/generic/tclIO.c
+++ b/generic/tclIO.c
@@ -397,9 +397,9 @@ ChanClose(
  *	    calling Tcl_GetErrno().
  *
  * Side effects:
- *	The CHANNEL_BLOCKED and CHANNEL_EOF flags of the channel state are set
- *	as appropriate.  On EOF, the inputEncodingFlags are set to perform
- *	ending operations on decoding.
+ *	The CHANNEL_ENCODING_ERROR, CHANNEL_BLOCKED and CHANNEL_EOF flags
+ *	of the channel state are set as appropriate.  On EOF, the
+ *	inputEncodingFlags are set to perform ending operations on decoding.
  *
  *	TODO - Is this really the right place for that?
  *
@@ -4661,6 +4661,12 @@ Tcl_GetsObj(
     char *dst, *dstEnd, *eol, *eof;
     Tcl_EncodingState oldState;
 
+    if (GotFlag(statePtr, CHANNEL_ENCODING_ERROR)) {
+	UpdateInterest(chanPtr);
+	Tcl_SetErrno(EILSEQ);
+	return TCL_INDEX_NONE;
+    }
+
     if (CheckChannelErrors(statePtr, TCL_READABLE) != 0) {
 	return TCL_INDEX_NONE;
     }
@@ -5031,6 +5037,7 @@ Tcl_GetsObj(
   done:
     assert(!GotFlag(statePtr, CHANNEL_EOF)
 	    || GotFlag(statePtr, CHANNEL_STICKY_EOF)
+	    || GotFlag(statePtr, CHANNEL_ENCODING_ERROR)
 	    || Tcl_InputBuffered((Tcl_Channel)chanPtr) == 0);
     assert(!(GotFlag(statePtr, CHANNEL_EOF|CHANNEL_BLOCKED)
 	    == (CHANNEL_EOF|CHANNEL_BLOCKED)));
@@ -6016,6 +6023,12 @@ DoReadChars(
 	}
     }
 
+    if (GotFlag(statePtr, CHANNEL_ENCODING_ERROR)) {
+	/* TODO: We don't need this call? */
+	UpdateInterest(chanPtr);
+	Tcl_SetErrno(EILSEQ);
+	return -1;
+    }
     /*
      * Early out when next read will see eofchar.
      *
@@ -10108,6 +10121,11 @@ DoRead(
      * too.  Keep on keeping on for now.
      */
 
+    if (GotFlag(statePtr, CHANNEL_ENCODING_ERROR)) {
+	UpdateInterest(chanPtr);
+	Tcl_SetErrno(EILSEQ);
+	return -1;
+    }
     if (GotFlag(statePtr, CHANNEL_STICKY_EOF)) {
 	SetFlag(statePtr, CHANNEL_EOF);
 	assert(statePtr->inputEncodingFlags & TCL_ENCODING_END);
@@ -10205,10 +10223,10 @@ DoRead(
 	    }
 
 	    /*
-	     * 1) We're @EOF because we saw eof char.
+	     * 1) We're @EOF because we saw eof char, or there was an encoding error.
 	     */
 
-	    if (GotFlag(statePtr, CHANNEL_STICKY_EOF)) {
+	    if (GotFlag(statePtr, CHANNEL_STICKY_EOF|CHANNEL_ENCODING_ERROR)) {
 		break;
 	    }
 
@@ -10293,6 +10311,7 @@ DoRead(
 
     assert(!GotFlag(statePtr, CHANNEL_EOF)
 	    || GotFlag(statePtr, CHANNEL_STICKY_EOF)
+	    || GotFlag(statePtr, CHANNEL_ENCODING_ERROR)
 	    || Tcl_InputBuffered((Tcl_Channel)chanPtr) == 0);
     assert(!(GotFlag(statePtr, CHANNEL_EOF|CHANNEL_BLOCKED)
 	    == (CHANNEL_EOF|CHANNEL_BLOCKED)));
@@ -11566,8 +11585,8 @@ DumpFlags(
     char *str,
     int flags)
 {
-    char buf[20];
     int i = 0;
+    char buf[24];
 
 #define ChanFlag(chr, bit)      (buf[i++] = ((flags & (bit)) ? (chr) : '_'))
 
@@ -11580,6 +11599,7 @@ DumpFlags(
     ChanFlag('c', CHANNEL_CLOSED);
     ChanFlag('E', CHANNEL_EOF);
     ChanFlag('S', CHANNEL_STICKY_EOF);
+    ChanFlag('U', CHANNEL_ENCODING_ERROR);
     ChanFlag('B', CHANNEL_BLOCKED);
     ChanFlag('/', INPUT_SAW_CR);
     ChanFlag('D', CHANNEL_DEAD);
diff --git a/tests/io.test b/tests/io.test
index ef9e14d..d5f10a5 100644
--- a/tests/io.test
+++ b/tests/io.test
@@ -9063,7 +9063,7 @@ test io-75.6 {invalid utf-8 encoding read is not ignored (-strictencoding 1)} -s
     lappend hd $msg
 } -cleanup {
     removeFile io-75.6
-} -result "41 0 {}" ; # Here, an exception should be thrown
+} -match glob -result {41 1 {error reading "*": illegal byte sequence}}
 
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